I have a two board. One is ls1021a-twr and other is ls1021a-iot.
When I modify UART part (uart 2, 3, 4) disabled -> okey in device tree file with ls1021a-twr, I can use uart 2, 3, 4.
But I can not use uart 2, 3, 4 in ls1021a-iot board.
I can see ttyS2, ttyS3, ttyS4. I can not send signal with minicom.
UART 2, 3, 4 is duplicated with LPUART1 (RXD, TXD, RTS, CTS) and LCD H-Sync, V-Sync signal.
In ls1021a-iot document page 12 : For full VSYNC/HSYNC support, the RCW needs to be updated to enable these signals and UART1 cannot be used. See the device errata for details.
For using UART, RCW must be modifyed?